Which one is better for efficient free text search, Hibernate Search or Lucene? - lucene

We are developing a web application using Spring MVC, Spring and Hibernate.
We need to add efficient free text search capabilities to our applications. For this we are thinking of using either Hibernate Search (it uses Lucene under the hood) or directly lucene.
What is the best option for us as we are already using hibernate in our application? What are the pros and cons of one over the other?
Thanks.


You said it yourself - you'll be using Lucene one way or the other.
The raw Lucene API isn't very easy to use. It's much more low-level than Hibernate Search. if you're already using Hibernate, then it's a no-brainer - use Hibernate Search to implement your text search functionality.


disclaimer: I'm one of the developers of Hibernate Search.
The goal of the project is not to compete with Lucene nor Solr, but to facilitate as much as possible integration with Hibernate applications, to avoid having to maintain the two worlds in sync and duplicate all mapping and CRUD operations.
While we provide some common helpers and a nice encapsulation, Hibernate Search can also hand you over a direct reference to the Lucene API, so in case you find yourself needing to use the "raw" Lucene API you will never be stuck. Also for writing to the index Hibernate Search provides a common pattern which will solve most of known requirements, but in case you have very non-standard requirements you can get full control of the written Documents.
Solr is a good alternative, but as it is a separate server you have to interact with it via REST APIs which is quite different, with it's pros and cons. Having a second service to manage is not always wanted, and of course the remote invocations will never be as efficient as direct references to Lucene and to all it's internal filters and caches.
Not all functionality of Lucene can be exposed via a remote API, and if you need to do some "low level" operation, if this is not implemented in Solr you won't be able to do it (without patching Solr). Still Solr is very cute, especially when you want to share the index with other non-Java applications, and so we might add a Solr backend for Hibernate Search to eventually keep a Solr server in synch (especially if there's interest for it, and possibly some help).
Finally, the Lucene API is really hard core stuff. We spend a lot of effort to make the best use of it to provide top performance while exposing a stable API to people using Hibernate Search, basically until now all releases have been backwards compatible to provide a "drop-in" performance boost to use latest greatest tricks from Lucene - which actually changes API quite often; these changes are always exciting, but be prepared to maintain that in your application if you don't use a proper abstraction.


The other way of using Lucene is to get the middlman API which is known as SOLR. SOLR will connect to Lucene and perfom HTTP calls for search. Please note that you will need to build and Parse the XML what Solr consumes. All the functionality of Lucene is exponse via SOLR and should be really helpful.

Related

When Lucene is preferred over Solr or ElasticSearch?

I know that Solr and ElasticSearch are wrappers over Lucene. Can you please give me some usecases where we would not prefer to use Solr or ElasticSearch, but would want to use Lucene?

Lucene is a search library built in Java while Solr and Elastic Search (ES) are web applications using Lucene under the hood.
In most cases you would prefer Solr or ES to Lucene mainly because of the out of the box mechanisms for: distributed search, replication, sharding and indexing management on multiple nodes.
As such mechanisms are hard to implement and maintain using your custom Java app and Lucene.
You would choose Lucene:
To have more control as it's only a jar that doesn't have strict dependencies;
you don't want to be constrained by any particular server;
you don't want to build the automation to deploy Solr or ES in production (with their server, security, eventually zookeeper etc...);
your index won't spawn on multiple nodes;
you're not concerned with development time (as Solr and ES would have many out of the box features compared to Lucene).
So in summary, if you want to have more control on your solution, you would use Lucene.

Can we customize Lucene which is embedded in Solr?

Can we customize Lucene which is embedded in Solr just as we can in raw Lucene ? So that we can have "everything" that we have in Lucene in Solr ?
I am asking this because we are stuck at a point of deciding Solr vs Lucene, thinking like so :
Argument 1 :
"We might hit a dead zone in future if
we choose Solr, and Lucene is a better
choice hence... So we might as well
start writing HTTP wrappers and almost
half of Solr ourselves on top of
Lucene to be on safer side. "
Argument 2 :
"Solr already has all the features we
want to use, so why not just use it ?
Since people who commit to Lucene are
also responsible for committing to
Solr, all features of Lucene are
available to Solr too..."
I went through many blogs and posts that say something like :
For situations where you have very customized requirements requiring
low-level access to the Lucene API classes, Solr would be more a
hindrance than a help, since it is an extra layer of indirection.
-http://www.lucenetutorial.com/lucene-vs-solr.html
One way of defending Argument 2 is by confirming that we can customize the underlying Lucene in Solr just like we would do if we had only Lucene.
Can someone provide a better way of closing this argument ? :)
ps : We need a fast search with indexing and sharding terabytes of data...

Can we customize Lucene which is embedded in Solr ?
Yes, you can. But keep this in mind:
Lucene and Solr committers are some of the foremost experts in the field of full-text search. They have several years of experience in this field. If you think you can do better than them, then go ahead and change Solr to your needs (it's Apache-licensed so there aren't any commercial restrictions), and if you do so try to do it so that you can later contribute it back to the project so everyone can benefit and the project moves forward.
For the vast majority of Solr users though, the stock product is more than enough and satisfies all needs.
In other words, before jumping in to change the code, ask on a mailing list (stackoverflow or solr-user), there's a good chance that you don't really need to change any code.
"Fast search with indexing and sharding terabytes of data" is precisely what Solr was built for. It would be a bad case of Not-Invented-Here not to use it or any of the other similar solutions, such as ElasticSearch, Sphinx, Xapian, etc. If you think you'll need to customize or extend the search server in any way, consider the license and underlying code of each one. Solr and ElasticSearch are both Apache-licensed so they don't have commercial restrictions and are built on top of Lucene, a well-known library.

Where do I begin learning Lucene.NET Solr Hadoop and MapReduce?

I'm a .NET developer and I need to learn Lucene so we can run a very large scale search service that removes entries that the end user doesn't have access to. (ie a User can search for all documents with clearance level 3 or higher, but not clearance level 2 or 1)
Where do I start learning, which products should I consider? To be honest, I'm a little overwhelmed, but I'm determined to figure it all out... eventually.

If you want a book that covers all the basics of Lucene, consider "Lucene in Action". Even though the code samples are Java, you can easily port them to .NET. Of course, there also are tonnes of resources on the web, such as SO and the Lucene mailing lists which should help you along.
For project you describe, you should look at Solr since it abstracts out lots of the issues of scalability etc. and via Solrnet can easily integrate into your .NET app. To restrict access by a level, your index documents should contain a field called "Level" (say) and in the background of your user query, you append the "Level:Level-1" query, using a boolean query construct.
At this stage, my recommendation would be to stay away from Hadoop (Apache Map-reduce implementation) for your project and stick with Solr. If you are however keen to learn about it. It too has a very useful book, you guessed it "Hadoop In Action" (also from Manning Publications).

You seem to be confused about what exactly each project (Lucene/Solr/Hadoop/etc) does. So the first thing to do would be understanding the purpose of each project. Read the docs and blogs about them. If possible, buy and read books about them.
For example, MapReduce and Hadoop have nothing to do with your security requirements. Hadoop is a platform for distributed, scalable computing. But Solr is scalable on its own. You might want to use Hadoop to distribute a crawler though (e.g. Nutch).

Solr or Nhibernate Search

Bit confused here,
How’s Solr or Solrnet any different from Nhibernate Search? Does Solr offer anything more to Lucene.net that Nhibernate Search?

I explained the differences and relationships between these projects in this blog post.
In a nutshell: while Lucene(.net) is a library, Solr is a stand-alone Java application that uses Lucene to provide full-text indexing and searching through a XML/HTTP interface. This means that it can be used from any platform/language. While very flexible, it's easier to use than raw Lucene and provides features commonly used in search applications, like faceted search and hit highlighting. It also handles caching, replication, sharding, and has a nice web admin interface. None of those features are directly provided by Lucene.net / NHibernate.Search.
SolrNet is a client to communicate with Solr from a .net application.

How do we create a simple search engine using Lucene, Solr or Nutch?

Our company has thousands of PDF documents. How do we create a simple search engine using Lucene, Solr or Nutch? We'll provide a basic Java/JSP web page were people can type in words and perform basic and/or queries then show them the document links of all matching PDF's.

I have had good luck with lucene, but it is not click, install and search, it does require a bit of work.
If you need something that yo can download and install and be searching within 10 minutes, look at the free Ominifind Yahoo Edition http://omnifind.ibm.yahoo.net/, it uses Lucene, but is packaged such that it is configured and ready to run upon install, a much easier way to try Lucene.

Nutch + Lucene + Pdf plugin enabled in Nutch is your solution. Nutch allows you to parse pdfs by enabling the pdf plugin.
Lucene will allow you to index the crawled and parsed data and Nutch has servelet which gives you a search interface.
We use the same for our internal lans.

None of the projects in the Lucene family can natively process PDFs, but there are utilities you can drop in and well written examples on how to roll your own.
Lucene will do pretty much whatever you need it to do, but there is overhead in terms of your time, as Tony said above. Thousands of documents really isn't that many, so you might be able to get away with a lighter weight alternative.
That said, I would still recommend looking at Solr - it's much, much easier to set up than Lucene, has support for backups, replication, etc., as well as a nifty JSON interface which would fit your use case very well: http://wiki.apache.org/solr/SolJSON

Google Search Appliance http://www.google.com/enterprise/gsa/

I think you want a system to manage your PDF file. Please try to use dspace system. Dspace is a digital library, it supports Lucene based on. www.dspace.org.

Take a look at eprints. It includes a workflow for adding new documents, automatically indexes and thumbnails PDF's and has fairly comprehensive full text search functionality. It can also be easily customised and branded.
Why re-invent the wheel. Again.

Answering such a broad question in this forum will be tough. I'd recommend you check out the book Lucene in Action, which covers the basics of indexing and searching in a quite readable fashion.
Given your application, it sounds like Nutch and Solr probably will not be necessary. Since all of your documents are available locally, Nutch probably won't be helpful. Solr may help you manage a cluster of searchers if you have a high query load, but Lucene is highly performant, and handles large document sets in a very scalable manner.
The one area that might consume a lot of your effort is the use of PDF. It's possible to index PDF documents, and there are Lucene contributions to facilitate the extraction of raw text from PDFs, but depending on the document, the quality of results can vary. Often, the context of a keyword in a PDF document is unclear because of formatting instructions, and that can make it hard to do proximity searches or show the context of a hit.

A great free search technology you might look at is the IBM Yahoo! free search. I'm not sure whether they followed through on plans to use Lucene under the covers, but it remains one of the really great, east to use free search technologies. It handles up to 500K documents, I believe, and it supports PDF and other non-text formats as well. Graphic user interface; easy to customize search results, and basic search analytics. Basic thesaurus, and powerful API so you can do pretty much whatever you want if the out of the box results are not to your liking. We've suggested this to a number of clients where there were fewer than half a million documents, and they love it.

If you've a Linux server, you could use Beagle to index them, and then just use the search functionality that comes with it. It has an (experimental) web search interface, and it can be hooked into the FireFox search box as well.
It automatically indexes files as they're included, and I'd suspect that you'll find it much more efficient to enhance or fix beagle than to write your own search interface to Lucene.

Having the (imho) distinct advantage of being on a Mac, I use SearchLight on a somewhat older G5. nice web interface to spotlight, the Mac OS' built-in indexing service.